Snodar at Dome A
Snodar 1 at Dome A

Snodar (Surface layer NOn-Doppler Acoustic Radar) is a site-testing instrument developed by our team specifically for Antarctica. It is designed to measure the height and intensity of the atmospheric boundary layer on the Antarctic plateau. The nature of the atmospheric boundary layer above the Antarctic plateau is of interest both to atmospheric scientists and to astronomers wishing to plan future optical telescopes. Snodar works by sending an intense acoustic pulse into the atmosphere and listening for backscatter off inhomogeneities resulting from temperature gradients and wind shear. The theory of operation is very similar to that of the well known underwater sounding techniques of SONAR.

We obtained a week of data in 2008. In 2009 we deployed a new Snodar and obtained excellent data until August 2009, when snow on the dish reduced the sensitivity. Snodar became operational again during 2010.

Snodar is a monostatic acoustic radar with a minimum sampling height of 5m, a range of at least 200m, a vertical resolution of 1m. Snodar operates at frequencies between 4kHz and 15kHz. Such high frequencies propagate relatively well in the low temperature of the Antarctic atmosphere.

Snodar fax plot A sample of Snodar data, updated weekly (if the instrument is operating), frequently showing a clear boundary-layer separation. The vertical axis of the plot spans 0 to 100 meters and the horizontal axis covers 12 hours. These data are uncalibrated; please contact the PLATO team for further information.

Snodar uses a single horn-loaded compression driver as both transmitter and receiver, and an off-axis parabolic dish to collimate the acoustic beam. The signal is acquired using a USB sound card. A PC/104 computer performs the signal processing in real time. Snodar runs autonomously, storing raw data on USB flash disks for retrieval the following summer, while uploading processed data via the Iridium satellite network. The Iridium communication also allows Snodar to be remotely controlled.

Snodar dish Snodar 1 dish and compression driver (credit: Colin Bonner)

Snodar is guarded from background noise by a heavily damped enclosure. The inside of enclosure is lined with material that absorbs nearly all the sound frequencies that can interfere with its correct operation.

Snodar Colin Bonner with the Snodar 1 enclosure (credit: Michael Ashley)

Refereed papers from Snodar

  1. C. S. Bonner, M.C.B. Ashley, X. Cui, L. Feng, X. Gong, J.S. Lawrence, D.M. Luong-Van, Z. Shang, J.W.V. Storey, L. Wang, H. Yan, J. Yang, X. Zhou and Z. Zhu, 2010, Thickness of the Atmospheric Boundary Layer Above Dome A, Antarctica, during 2009, Publications of the Astronomical Society of the Pacific, 122, 1122–1131.
  2. Yang, H., Allen, G., Ashley, M.C.B., Bonner, C.S., Bradley, S., Cui, X., Everett, J.R., Feng, L., Gong, X., Hengst, S., Hu, J., Jiang, Z., Kulesa, C.A., Lawrence, J.S., Li, Y., Luong-Van, D., McCaughrean, M.J., Moore, A.M., Pennypacker, C., Qin, W., Riddle, R., Shang, Z., Storey, J.W.V., Sun, B., Suntzeff, N., Tothill, N.F.H., Travouillon, T., Walker, C.K., Wang, L., Yan, J., Yang, J., York, D., Yuan, X., Zhang, X., Zhang, Z., Zhou, X., and Zhu, Z., 2009, The PLATO Dome A Site-Testing Observatory: Instrumentation and First Results, Publications of the Astronomical Society of the Pacific, 121, 174–184.
  3. C.S. Bonner, M.C.B. Ashley, J.S. Lawrence, D.M. Luong-Van, and J.W.V. Storey, 2009, Snodar: An acoustic radar for atmospheric turbulence profiling with 1m resolution, Acoustics Australia, 37, 47–51.

SPIE instrumentation papers from Snodar

  1. Colin S. Bonner, Michael C. B. Ashley, Stuart G. Bradley, Xiangqun Cui, LongLong Feng, Xuefei Gong, Jon S. Lawrence, Daniel M. Luong-Van, Zhaohui Shang, John W. V. Storey, Lifan Wang, Huigen Yang, Ji Yang, Xu Zhou, and Zhenxi Zhu, 2010, Snodar: 2009 performance at Dome A, Antarctica, Proc. SPIE, 7733, 77334A–77334A-6.
  2. C.S. Bonner, M.C.B. Ashley, J.S. Lawrence, J.W.V. Storey, D.M. Luong-Van and S.G. Bradley, 2008, Snodar: a new instrument to measure the height of the atmospheric boundary layer on the Antarctic plateau, Proc. SPIE, 7014, 70146I– 70146I-7.

Conference proceedings from Snodar

  1. J.S. Lawrence, M.C.B. Ashley, C.S. Bonner, S. Bradley, D. Luong-Van, and J.W.V. Storey, 2007, Characterisation of The Dome C atmospheric boundary layer turbulence with a non-Doppler acoustic radar, (Eds N. Epchtein and M. Candidi), EAS Publications Series, 25, 31–34.
  2. C.S. Bonner, M.C.B. Ashley, J.S. Lawrence, D.M. Luong-Van, and J.W.V. Storey, 2008, Snodar II: Probing the atmospheric boundary layer on the Antarctic Plateau, Conference Proceedings of the Imperial College Press World Scientific, Sardegna, Italy, September, 2008.


Primary designer and constructor: Colin Bonner
Principal Investigator: Professor Michael Ashley

Participating institutions in alphabetical order

Auckland University of Auckland, NZ
UNSW University of New South Wales, Australia